Inhalant Anesthesia Flashcards

1
Q

What are the cons of inhalant anesthesia?

A
  1. Specialized (expensive) equipment needed

2. Equipment can fail (need monitoring and expertise)

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2
Q

T/F. The dosage for inhalant anesthetic drugs is expressed as a concentration (VOLUME %) of the whole gas mixture. Can be discussed as INSPIRED FRACTION (FI) of the drug.

A

True

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3
Q

Most inhalant anesthetics are VAPORS. What does a vapor refer to?

A

Gaseous state of a substance that at ambient temperature and pressure is a liquid.

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4
Q

T/F. Because the vapor pressure for different drugs varies, the vaporizer does not have to be matched to the specific drug.

A

False.

The vaporizer HAS to be matched to the specific drug.

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5
Q

Which of the following is INCORRECT about solubility of inhalant anesthesia?

A. Blood/Gas solubility coefficient is the most clinically relevant measure of solubility.
B. The more soluble the anesthetic agent, the shorter it will take to reach equilibrium.
C. A more soluble drug will want to get in the blood and spend more time in the blood (the blood is acting like a sponge that is soaking up the anesthetic drug.
D. The more insoluble the agent, the faster it will reach equilibrium.

A

B. The more soluble the anesthetic agent, the shorter it will take to reach equilibrium.

The more soluble the anesthetic agent (higher blood/gas coefficient), the LONGER it will take to reach equilibrium (slower induction, recovery, and response to changes in dose).

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6
Q

T/F. Halothane has a blood/gas coefficient of 2.4. This means that the concentration of halothane dissolved in the blood will be 2.4 times less than the concentration in gas form (in the alveolus) at equilibrium.

A

False.

2.4 times GREATER than the concentration in gas form at equilibrium.

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7
Q

T/F. Desflurane has a blood/gas coefficient of 0.45 so at equilibrium, the concentration dissolved in blood will only be 0.45 times that in the alveolus.

A

True

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8
Q

Why would a more insoluble drug in blood will rise and fall rapidly compared to a more soluble drug?

A. The premise is false; a more insoluble drug in blood will NOT rise and fall more rapidly.
B. A more insoluble drug will more readily move into blood and less readily leave the blood.
C. A more insoluble drug will less readily move into blood and more readily leave the blood.

A

C. A more insoluble drug will less readily move into blood and more readily leave the blood.

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9
Q

What would happen if an anesthetic drug is completely insoluble?

A

It would never enter the bloodstream/tissues ad thus be USELESS!

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10
Q

What does MAC stand for? What is it?

A

Minimum Alveolar Concentration.
The equilibrium concentration of an anesthetic in the alveolus that is required to prevent movement and response to pain 50% of individuals (similar to an anesthetic ED50).

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11
Q

Which of the following statement regarding MAC is FALSE?

A. Vary between different drugs and between different species for the same drug.
B. If 1.3MAC is needed for anesthetic maintenance and a particular inhalant is 1.5%, you would set your vaporizer to 2%.
C. Required amount of inhalant will change based on the patient’s physiologic status or the presence of other drugs.
D. None of the above.
E. All of the above.

A

D. None of the above

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12
Q

What are the pros of inhalant anesthetic drugs?

A
  1. Control of the airway and ventilation

2. Control over drug uptake and elimination

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13
Q

T/F. The pharmacokinetics of inhalant anesthetic is very different than most drugs because it occurs primarily via the lungs.

A

True.

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14
Q

Which of the following is INCORRECT about ABSORPTION relating to inhalant anesthetics pharmacokinetics?
A. Absorption happens completely through the lungs at the level of the alveolus.
B. Gas needs to reach the alveoli > diffuse across the alveolus into capillaries.
C. Gas concentration in the alveoli = Gas concentration in the bloodstream.
D. If there is a disease in the lung, normal diffusion will be increased.
E. If the lung perfusion is reduced (decreased CO), absorption will be impaired.

A

D. If there is a disease in the lung, normal diffusion will be increased.

If there is a disease in the lung, normal diffusion will be decreased (not as effective).

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15
Q

Which of the following statement is INCORRECT about DISTRIBUTION relating to Inhalant anesthetic pharmacokinetics?
A. Distribution is generally good for anesthetic agents (all lipid soluble to cross BBB).
B. We expect to have a reduction phase (higher rates of inhalant are needed until the tissue reservoirs have filled and equilibrium is reached).
C. After a few minutes of delivery, it can be turned down to maintain blood and tissue (brain) levels (maintenance phase).
D. Inhalant anesthetics will cross the placenta.

A

B. We expect to have a reduction phase (higher rates of inhalant are needed until the tissue reservoirs have filled and equilibrium is reached).

AN INDUCTION PHASE > can be turned down to maintenance phase.

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16
Q

T/F. All inhalant anesthetics have the same metabolism.

A

False.

Variable between different anesthetic agents (most common agents undergoing no metabolism).

17
Q

T/F. Excretion is primarily via the kidney.

A

False.

Excretion is primarily via the LUNGS.

18
Q

What are the general pharmacologic effects of inhalant anesthetics on CNS?

A

CNS: Dose-dependent CNS depression (NO analgesia, YES pain and muscle relaxation).
Vasodilation (UP intracranial pressure) and control seizure activity.

19
Q

What are the general pharmacologic effects of inhalant anesthetics on respiratory?

A

Respiratory: dose-dependent respiratory depression (RISE in CO2 and DOWN in O2).
Bronchodilation (halothane, isoflurane, sevoflurane, desflurane)
Airway irritation in primates (desflurane)

20
Q

What are the general pharmacologic effects of inhalant anesthetics on Cardiovascular?

A

Dose-dependent cardiovascular depression.
DOWN myocardial contractility.
Vasodilation > HYPOtension.
Pro-arrhythmic effects.

21
Q

What are the general pharmacologic effects of inhalant anesthetics on Liver?

A

DOWN hepatic blood flow.

22
Q

What are the general pharmacologic effects of inhalant anesthetics on Renal?

A

DOWN renal blood flow (GFR).

23
Q

What are the general pharmacologic effects of inhalant anesthetics on Muscle?

A
MILD muscle relaxation and UP competitive neuromuscular blockers.
Malignant hyperthermia (halothane), therefore, Dantrolene is the typical treatment.
24
Q

What are the general pharmacologic effects of inhalant anesthetics on Body temp?

A

HYPOTHERMIA (vasodilation) and IMPAIRED shivering (reduced heat production).

25
Q

Which of the statement is CORRECT about Halothane (Fluothane)?
A. Most commonly used.
B. 20% is eliminated through respiration and rest will eliminated through liver/kidney (parent drug or metabolites).
C. Blood/gas coefficient of 2.4 (fast induction and recovery).
D. Most potent cerebral vasodilator (increased ICP) and most arrhythmogenic and potential trigger for malignant hyperthermia.
E. A preservative thymol should be kept inside the vaporizers and be maintained.

A

D. Most potent cerebral vasodilator (increased ICP) and most arrhythmogenic and potential trigger for malignant hyperthermia.

  • Rarely used now.
  • 60-80% eliminated through respiration and rest eliminated through liver/kidney (parent drug or metabolites).
  • Blood/gas coefficient of 2.4 (slow induction and recovery).
  • A preservative thymol can be build up in vaporizers and they need to be drained regularly.
26
Q

Which of the following is CORRECT about Isoflurane (Isoflo)?
A. Rarely used inhalant anesthetic.
B. It has a higher blood/gas coefficient than Halothane and thus more rapid onset of anesthesia, recovery, and response to dose adjustments.
C. Isoflurane undergoes metabolism (99.8%).
D. Affects on all systems worse than halothane.
E. Enhancement of the effect of neuromuscular blockers is greater than with halothane.

A

E. Enhancement of the effect of neuromuscular blockers is greater than with halothane.

  • Most commonly used.
  • Lower blood/gas coefficient (1.4) > more rapid onset of anesthesia, recovery, and response to dose adjustments.
  • DOES NOT undergo metabolism (0.2%).
  • Affects on all systems are less than halothane.
27
Q

Which of the following is a CORRECT statement regarding Sevoflurane (SevoFlo)?
A. It has a higher blood/gas coefficient than isoflurane and so less rapid onset and recovery.
B. It causes more severe respiratory and cardiovascular depression than isoflurane and more enhancing effects of competitive NMBs.
C. It causes more cerebral vasodilation than isoflurane or desflurane.
D. Sevoflurane is the other most commonly used inhalant (with isoflurane).

A

D. Sevoflurane is the other most commonly used inhalant (with isoflurane).

  • lower blood/gas coefficient (0.65) than isoflurane and so MORE rapid onset and recovery.
  • Similar respiratory and cardiovascular depression than isoflurane and similar enhancing effects of competitive NMBs.
  • Less cerebral vasodilation than isoflurane or desflurane.
28
Q

T/F. Low flow rates of sevoflurane can react with soda lime adsorbent (used to collect CO2) and cause formation of a compound A, a potential nephrotoxin.

A

True.

29
Q

Which of the following is a CORRECT statement about Desflurane (Suprane)?
A. Desflurane has a higher vapor pressure than the others so do not need a specialized vaporizer.
B. Causes more respiratory depression than isoflurane.
C. Higher cardiovascular effects and higher effects on competitive NMBs, muscle relaxation, liver blood flow than isoflurane.
D. Alters renal blood flow.
E. Has the highest blood/gas coefficient out of all anesthetics so it is more advantageous in veterinary medicine.

A

B. Causes more respiratory depression than isoflurane.

  • Has a higher vapor pressure than the other so DO NEED a specialized vaporizer (heated, closed delivery system).
  • Similar effects on cardiovascular, competitive NMBs, muscle relaxation, liver blood flow as isoflurane.
  • DOES NOT alter renal blood flow.
  • Has the LOWEST blood/gas coefficient out of all anesthetics but not used more than iso/sevo in vet med.
30
Q

Which of the following is a CORRECT statement regarding Nitrous Oxide (N2O)?
A. Aka “laughing gas” is the only current inhalant that is liquid.
B. Has a high blood/gas coefficient.
C. It has a very high MAC thus it is a potent inhalant.
D. NO analgesia, good muscle relaxer, common cardiovascular/respiratory depression seen with hepatic/renal damage.
E. Increases cerebral blood flow and ICP so do not use it in patients with a head trauma.
F. It is not easily diffused into air-filled spaces and does not expand the gas volume there.

A

E. Increases cerebral blood flow and ICP so do not use it in patients with a head trauma.

  • Aka “laughing gas” is the only current inhalant that is actually a GAS (gas in room temperature).
  • Low blood/gas coefficient (0.47).
  • high MAC thus it is NOT a potent inhalant (adjunct along with another inhalant and be ran at 66%).
  • Provides analgesia (only inhalant that does this!), a poor muscle relaxer, minimal cardiovascular/respiratory depression and has minimal hepatic/renal effects.
  • Easily diffused into air-filled spaced and causes expansion of the gas volume there.
31
Q

What is “second gas effect”? Which inhalant anesthetic is involved?

A

Nitrous oxide.
Because N2O is highly soluble and it is a gas, a higher volume of gas is moving into the alveolus to equilibrate with the blood > other gases being delivered with N2O will be moved into the alveolus more rapidly and CLINICALLY FASTER INDUCTION IS SEEN.

32
Q

What is Diffusion Hypoxia (FINK EFFECT)? Which inhalant anesthetic is involved?

A

Nitrous oxide.
During recovery (delivery ceases), Nitrous in the body will diffuse out and occupy space within the alveolus > displace other gases in the alveolus (O2) > HYPOXIA.
Need to give 100% O2 on recovery.

33
Q

What are other delivery methods for inhalation anesthetics?

A

Boxing down, masking down, intranasal cannula.

Animals that are too fractious to gain IV access, animals with no veins, tiny animals, neonatal animals, C-section.

34
Q

What are the inhalant anesthetics that are important in vet med?

A

Halothane, Isoflurane, Sevoflurane, Desflurane, Nitrous Oxide